Grant: Discovery Grants Program - Individual

Our research program will first look at chemical and physical recycling strategies for polymers. With the exception of polyesters, commodity polymers are not chemically depolymerizable to the monomer level. Chemical depolymerization of polyolefins, for example, is particularly challenging due to a) the endergonic nature of the reaction and b) the extraordinary stability of the chemical bonds forming the polymers. We will demonstrate that heterogeneous photocatalysis is particularly suitable to promote the depolymerization of main commodity polymers such as polyolefins as the catalyst is able to generate high energy intermediates that can attack the most stable substrates. Over the years, we have developed various techniques to boost the photocatalytic activity of inorganic photocatalysts using plasmonic nanoparticles. Such catalysts are sufficiently powerful to promote nondirected alkane oxydation. This photocatalytic reaction will generate a weak link within the polymer backbone which will be used as starting point to promote depolymerization via a zip type mechanism. As an alternative, we will also evaluate the possibility of preparing commodity polymers that contain weak links that can be used to trigger a chemical depolymerization. In order to be meaningful, it is important to design weak links that do no significantly alter the physical and mechanical properties of the polymer, and which remain sufficiently stable for most uses, but which can nonetheless be used as entry point to promote the degradation. We expect that the resulting polymers will be degradable and under certain conditions will be able to regenerate the starting monomers.  We will also scrutinize the possibility of mechanically recycling polymers without employing elevated temperatures. Mechanical recycling (reprocessing) of thermoplastics nearly always require elevated temperatures which damage the chemical backbones of the polymers. Thus most polymers can only be down-cycled.  Baroplastic copolymers are polymers that can be processed at ambiant temperature using pressure. In this proposal, we will present new strategies to synthesize baroplastic polymers. Notably, we hope that the recycling of polyvinylchoride (PVC) could become possible via this strategy. We will also investigate the possible auxetic characteristics of baroplastic polymers.  Auxetic materials have a negative Poisson ratio. To date, no organic material is exhibit at the molecular level. We believe that under certain conditions baroplastic materials could become auxetic, opening the door to a world of unusual mechanical properties that are not encountered in any other molecular material.